The present invention relates to motor vehicles and more particularly to headlight beam control systems of motor vehicles, in which a beam of each headlight is selectively adjustable to one of a plurality of predetermined positions as angled from the horizonal of a vehicle body under the control of a manually operable controller mounted within the vehicle passenger compartment.
Conventionally, it is proposed, for the purpose of reducing accident due to dazzling of a driver of an oncoming vehicle, to provide a headlight beam control system in which the inclination of a vehicle body relative to the road surface is detected by measuring a distance between the vehicle body and a front axle and a distance between the vehicle body and a rear axle, and a beam of each headlight is automatically adjusted to an appropriate one of a plurality predetermined positions as angled from the horizontal of the vehicle body in response to the detected vehicle body inclination. Such an automatic headlight beam control system, however, has a disadvantage that a device employed in the system to detect the inclination of the vehicle body, which stretches from the front axle to the rear axle, is bulky, heavy in weight and expensive. Therefore, such a bulky system that uses this kind of detecting device is not suitable for passenger automobiles in which variation of the vehicle inclination ranges from 0.04 to 0.05 in terms of tan .theta.. Accordingly, in the case of passenger automobiles, the objective to control a beam of each headlight so as to prevent dazzling of a driver of an oncoming vehicle could be accomplished by adjusting each headlight angularly under the control of a manually operable controller mounted within a passenger compartment.
Based on this recognition it has been proposed by the applicants of this application to adjust a beam of each headlight to one of a plurality predetermined angular positions (as angled from the vehicle body's horizontal) in response to a selected one of a plurality, corresponding in number to the plurality of angular positions, positions of a manually operable controller via a suitable mechanism. With this proposal, since the use of a device, as described above, to detect the inclination of a vehicle body is eliminated, a headlight beam control system of a simple construction and of an accurate operation can be provided.
One of systems embodying this proposal has two drive motors disposed adjacent right and left headlight assemblies, respectively, to move the headlights angularly via respective linkages. The fact that two drive motors are needed is inferior in construction and cost. Besides, it is difficult to find enough room adjacent the headlight assemblies for installation of these motors. To avoid the latter mentioned problem, it is possible to replace these two motors with a single two-directional drive motor remotely installed from and operatively connected (via a wire and pulley linkage) to headlight. This, however, has a problem that the two-directional drive motor is expensive.